Get best of the week

Recetas PostgreSQL: obtenga tipos de columna en una consulta

Para preparar la obtención de tipos de columna en una solicitud, necesitamos postgres . También puedes usar la imagen terminada .

Me apresuro a decepcionar de inmediato: ¡la implementación no estará en SQL! Aunque, terminado, y hay funciones adecuadas. Pero el código resultante me pareció demasiado complicado y feo, y por lo tanto, implementé todo en ... C! Es cierto, desafortunadamente, no como una extensión, sino como una modificación de la fuente.

Aquí, de hecho, el parche en sí mismo para agregar tipos de columna a los nombres (para clientes versiones 2 y 3), con comentarios

diff --git a/src/backend/access/common/printtup.c b/src/backend/access/common/printtup.c
index 24d6cd0249..6862b69258 100644
--- a/src/backend/access/common/printtup.c
+++ b/src/backend/access/common/printtup.c
@@ -22,6 +22,9 @@
 #include "utils/lsyscache.h"
 #include "utils/memdebug.h"
 #include "utils/memutils.h"
+#include "utils/guc.h"        // 
+#include "utils/syscache.h"   // 
+#include "catalog/pg_type.h"  // 
 
 
 static void printtup_startup(DestReceiver *self, int operation,
@@ -70,6 +73,8 @@ typedef struct
 	MemoryContext tmpcontext;	/* Memory context for per-row workspace */
 } DR_printtup;
 
+static bool append; //     ?
+
 /* ----------------
  *		Initialize: create a DestReceiver for printtup
  * ----------------
@@ -132,6 +137,7 @@ printtup_startup(DestReceiver *self, int operation, TupleDesc typeinfo)
 {
 	DR_printtup *myState = (DR_printtup *) self;
 	Portal		portal = myState->portal;
+	append = GetConfigOption("config.append_type_to_column_name", true, true) != NULL; //         ?
 
 	/*
 	 * Create I/O buffer to be used for all messages.  This cannot be inside
@@ -236,6 +242,7 @@ SendRowDescriptionCols_3(StringInfo buf, TupleDesc typeinfo, List *targetlist, i
 	 * character set overhead.
 	 */
 	enlargeStringInfo(buf, (NAMEDATALEN * MAX_CONVERSION_GROWTH /* attname */
+							+ (append ? NAMEDATALEN * MAX_CONVERSION_GROWTH + sizeof("::") - 1 : 0) //       ,       
 							+ sizeof(Oid)	/* resorigtbl */
 							+ sizeof(AttrNumber)	/* resorigcol */
 							+ sizeof(Oid)	/* atttypid */
@@ -283,6 +290,17 @@ SendRowDescriptionCols_3(StringInfo buf, TupleDesc typeinfo, List *targetlist, i
 		else
 			format = 0;
 
+		if (append) { //       , 
+			HeapTuple typeTuple = SearchSysCache1(TYPEOID, ObjectIdGetDatum(att->atttypid)); //     
+			StringInfoData buf_; //    
+			initStringInfo(&buf_); //  
+			appendStringInfo(&buf_, "%s::", NameStr(att->attname)); //      ,   
+			if (HeapTupleIsValid(typeTuple)) appendStringInfoString(&buf_, NameStr(((Form_pg_type) GETSTRUCT(typeTuple))->typname)); //    ,     
+			else appendStringInfo(&buf_, "%i", att->atttypid); //     oid
+			pq_writestring(buf, buf_.data); //   
+			ReleaseSysCache(typeTuple); //  
+			pfree(buf_.data); //   
+		} else //          ,    -
 		pq_writestring(buf, NameStr(att->attname));
 		pq_writeint32(buf, resorigtbl);
 		pq_writeint16(buf, resorigcol);
@@ -311,6 +329,17 @@ SendRowDescriptionCols_2(StringInfo buf, TupleDesc typeinfo, List *targetlist, i
 		/* If column is a domain, send the base type and typmod instead */
 		atttypid = getBaseTypeAndTypmod(atttypid, &atttypmod);
 
+		if (append) { //       , 
+			HeapTuple typeTuple = SearchSysCache1(TYPEOID, ObjectIdGetDatum(att->atttypid)); //     
+			StringInfoData buf_; //    
+			initStringInfo(&buf_); //  
+			appendStringInfo(&buf_, "%s::", NameStr(att->attname)); //      ,   
+			if (HeapTupleIsValid(typeTuple)) appendStringInfoString(&buf_, NameStr(((Form_pg_type) GETSTRUCT(typeTuple))->typname)); //    ,     
+			else appendStringInfo(&buf_, "%i", att->atttypid); //     oid
+			pq_sendstring(buf, buf_.data); //   
+			ReleaseSysCache(typeTuple); //  
+			pfree(buf_.data); //   
+		} else //          ,    -
 		pq_sendstring(buf, NameStr(att->attname));
 		/* column ID only info appears in protocol 3.0 and up */
 		pq_sendint32(buf, atttypid);
diff --git a/src/backend/tcop/postgres.c b/src/backend/tcop/postgres.c
index 6c2db93573..f23de7f788 100644
--- a/src/backend/tcop/postgres.c
+++ b/src/backend/tcop/postgres.c
@@ -992,6 +992,8 @@ exec_simple_query(const char *query_string)
 	bool		use_implicit_block;
 	char		msec_str[32];
 
+	SetConfigOption("config.append_type_to_column_name", NULL, PGC_USERSET, PGC_S_SESSION); //    SQL-   ,     ,     
+
 	/*
 	 * Report query to various monitoring facilities.
 	 */
@@ -1959,6 +1961,8 @@ exec_execute_message(const char *portal_name, long max_rows)
 	bool		was_logged = false;
 	char		msec_str[32];
 
+	SetConfigOption("config.append_type_to_column_name", NULL, PGC_USERSET, PGC_S_SESSION); //      SQL-   ,     ,     
+
 	/* Adjust destination to tell printtup.c what to do */
 	dest = whereToSendOutput;
 	if (dest == DestRemote)

Bueno, y una bonificación, un parche similar para agregar tipos de columna a los nombres al convertir a json

diff --git a/src/backend/utils/adt/json.c b/src/backend/utils/adt/json.c
index 26d293709a..fb025adf58 100644
--- a/src/backend/utils/adt/json.c
+++ b/src/backend/utils/adt/json.c
@@ -32,6 +32,7 @@
 #include "utils/jsonapi.h"
 #include "utils/typcache.h"
 #include "utils/syscache.h"
+#include "utils/guc.h" //   
 
 /*
  * The context of the parser is maintained by the recursive descent
@@ -106,6 +107,8 @@ static void add_json(Datum val, bool is_null, StringInfo result,
 					 Oid val_type, bool key_scalar);
 static text *catenate_stringinfo_string(StringInfo buffer, const char *addon);
 
+static bool append; //     ?
+
 /* the null action object used for pure validation */
 static JsonSemAction nullSemAction =
 {
@@ -1789,6 +1792,17 @@ composite_to_json(Datum composite, StringInfo result, bool use_line_feeds)
 		needsep = true;
 
 		attname = NameStr(att->attname);
+		if (append) { //       , 
+			HeapTuple typeTuple = SearchSysCache1(TYPEOID, ObjectIdGetDatum(att->atttypid)); //     
+			StringInfoData buf; //    
+			initStringInfo(&buf); //  
+			appendStringInfo(&buf, "%s::", attname); //      ,   
+			if (HeapTupleIsValid(typeTuple)) appendStringInfoString(&buf, NameStr(((Form_pg_type) GETSTRUCT(typeTuple))->typname)); //    ,     
+			else appendStringInfo(&buf, "%i", att->atttypid); //     oid
+			escape_json(result, buf.data); //  
+			ReleaseSysCache(typeTuple); //  
+			pfree(buf.data); //   
+		} else //          ,    -
 		escape_json(result, attname);
 		appendStringInfoChar(result, ':');
 
@@ -1848,6 +1862,7 @@ array_to_json(PG_FUNCTION_ARGS)
 {
 	Datum		array = PG_GETARG_DATUM(0);
 	StringInfo	result;
+	append = GetConfigOption("config.append_type_to_column_name", true, true) != NULL; //         ?
 
 	result = makeStringInfo();
 
@@ -1865,6 +1880,7 @@ array_to_json_pretty(PG_FUNCTION_ARGS)
 	Datum		array = PG_GETARG_DATUM(0);
 	bool		use_line_feeds = PG_GETARG_BOOL(1);
 	StringInfo	result;
+	append = GetConfigOption("config.append_type_to_column_name", true, true) != NULL; //         ?
 
 	result = makeStringInfo();
 
@@ -1881,6 +1897,7 @@ row_to_json(PG_FUNCTION_ARGS)
 {
 	Datum		array = PG_GETARG_DATUM(0);
 	StringInfo	result;
+	append = GetConfigOption("config.append_type_to_column_name", true, true) != NULL; //         ?
 
 	result = makeStringInfo();
 
@@ -1898,6 +1915,7 @@ row_to_json_pretty(PG_FUNCTION_ARGS)
 	Datum		array = PG_GETARG_DATUM(0);
 	bool		use_line_feeds = PG_GETARG_BOOL(1);
 	StringInfo	result;
+	append = GetConfigOption("config.append_type_to_column_name", true, true) != NULL; //         ?
 
 	result = makeStringInfo();
 
@@ -1917,6 +1935,7 @@ to_json(PG_FUNCTION_ARGS)
 	StringInfo	result;
 	JsonTypeCategory tcategory;
 	Oid			outfuncoid;
+	append = GetConfigOption("config.append_type_to_column_name", true, true) != NULL; //         ?
 
 	if (val_type == InvalidOid)
 		ereport(ERROR,
@@ -1945,6 +1964,7 @@ json_agg_transfn(PG_FUNCTION_ARGS)
 				oldcontext;
 	JsonAggState *state;
 	Datum		val;
+	append = GetConfigOption("config.append_type_to_column_name", true, true) != NULL; //         ?
 
 	if (!AggCheckCallContext(fcinfo, &aggcontext))
 	{
@@ -2046,6 +2066,7 @@ json_object_agg_transfn(PG_FUNCTION_ARGS)
 				oldcontext;
 	JsonAggState *state;
 	Datum		arg;
+	append = GetConfigOption("config.append_type_to_column_name", true, true) != NULL; //         ?
 
 	if (!AggCheckCallContext(fcinfo, &aggcontext))
 	{

Bueno, ¿por qué hice todo esto? Porque puedo aunque, no solo, tengo una idea interesante de cómo se puede usar de manera efectiva, pero hasta ahora mis manos no han llegado ...

Ejemplo
set config.append_type_to_column_name = true;
with s as (
    select * from task
) select json_agg(s) from s
[{"id::int8":1,"parent::int8":null,"dt::timestamptz":"2020-05-20T07:53:03.952542+05:00","start::timestamptz":"2020-05-20T07:53:04.930703+05:00","stop::timestamptz":"2020-05-20T07:53:04.976998+05:00","group::text":"group","max::int4":null,"pid::int4":5905,"request::text":"select now()","response::text":"2020-05-20 07:53:04.976151+05","state::state":"DONE","timeout::interval":null,"delete::bool":false,"repeat::interval":null,"drift::bool":true,"count::int4":null,"live::interval":null,"remote::text":null,"append::bool":false,"header::bool":true,"string::bool":true,"null::text":"\\N","delimiter::char":"\t","quote::char":null,"escape::char":null},  {"id::int8":2,"parent::int8":null,"dt::timestamptz":"2020-05-20T07:53:12.780313+05:00","start::timestamptz":"2020-05-20T07:53:13.299168+05:00","stop::timestamptz":"2020-05-20T07:53:13.352304+05:00","group::text":"group","max::int4":null,"pid::int4":5908,"request::text":"select 1","response::text":"1","state::state":"DONE","timeout::interval":null,"delete::bool":false,"repeat::interval":null,"drift::bool":true,"count::int4":null,"live::interval":null,"remote::text":null,"append::bool":false,"header::bool":true,"string::bool":true,"null::text":"\\N","delimiter::char":"\t","quote::char":null,"escape::char":null},  {"id::int8":3,"parent::int8":null,"dt::timestamptz":"2020-05-20T07:53:15.954607+05:00","start::timestamptz":"2020-05-20T07:53:16.477578+05:00","stop::timestamptz":"2020-05-20T07:53:16.536582+05:00","group::text":"group","max::int4":null,"pid::int4":5910,"request::text":"select 1/0","response::text":"elevel\t20\noutput_to_server\ttrue\nfilename\tint.c\nlineno\t822\nfuncname\tint4div\ndomain\tpostgres-12\ncontext_domain\tpostgres-12\nsqlerrcode\t33816706\nmessage\tdivision by zero\nmessage_id\tdivision by zero\nROLLBACK","state::state":"FAIL","timeout::interval":null,"delete::bool":false,"repeat::interval":null,"drift::bool":true,"count::int4":null,"live::interval":null,"remote::text":null,"append::bool":false,"header::bool":true,"string::bool":true,"null::text":"\\N","delimiter::char":"\t","quote::char":null,"escape::char":null}]

More articles:


All Articles